1. Field of the Invention
This invention relates to efficient, safe and comfortable 2-seat vehicles for daily personal transportation, and particularly, to the use of center-tracking vehicle with retractable support side wheels to prevent turning over during normal use and during collision. More specifically, the major emphases of this particular 2-seat vehicle will be on the minimal utilization of roadway and parking spaces to fight traffic congestion as well as low aerodynamic drag and low curb weight for much improved fuel efficiency and low exhaust emission.
2. Description of the Prior Art
Two-wheeled, or center-tracking vehicles, such as bicycles and motorcycles have long been commercially used to achieve the above mentioned objectives. However, it is obvious that they do not offer the level of comfort and protection, both from the weather elements and during event of a collision, acceptable to the general public in more developed countries. Furthermore, touring motorcycles do not offer a significant improvement in gas mileage in comparison to an economy sized automobile, because of their lack of aerodynamic efficiency imposed by the fully-exposed body of the rider.
Full-bodied center-tracking vehicles have been described in various patents. These vehicles require means for stabilization against falling-over when stopped, moving at low speeds, or when moving on wet or otherwise slippery roadways, the latter condition cause tire slip to occur.
One prior art technique of stabilizing single track vehicles is to use a large passive gyro and utilize its precessional moment to control body roll. In U.S. Pat. No. 3,465,840 to Summers for example, the vehicle is stabilized against rolling over by a large brute force gyro having a lateral spin axis and a vertical gimbal axis. Roll equilibrium is maintained by application of a vehicle righting gimbal force as a function of gimbal precession rate. Gimbal drift resulting in gimbal displacement is erased by application of a drift correcting gimbal torque in the direction of the displacement. While the method disclosed in Summers has met with some success in stabilizing large ships, the weight, expense and complexity of this method have barred two wheeled vehicles from using the method in an economical manner.
A second type of stabilizing method which has been described in previous patents uses retractable outrigger wheels of various designs and mechanisms. U.S. Pat. No. 3,700,059 to Sutton discloses a vehicle stabilizing system wherein the outrigger wheels can be steered in the direction of travel, rotated to meet road speed and raised or lowered through an electromechanical system. Drawbacks to this design involve its great mechanical complexity thus increasing manufacturing cost, its completely exposed outrigger wheels mechanism along both sides of the vehicle, thus taking up almost as much road space as a conventional automobile thus offering no advantage in term of space saving ability, and furthermore, the fully exposed outrigger mechanism creates a large amount of wind drag thus offering little advantage in fuel economy over that of an economy car.
In U.S. Pat. No. 4,513,837 to Archer, the outrigger device is completely retractable upward in the vehicle's body cleanly. However, this cleanly upward retractable mechanism can only permit a narrow outrigger support track which makes the vehicle vulnerable to rolling over in slippery road condition or at high banking angle, and once the vehicle is rolled over on its side, there is no mechanism built in that can immediately right itself up, thus creating a very vulnerable situation where it can be run over by other cars. Furthermore, Archer's outrigger mechanism is placed not in the same saggittal plane with the center of gravity (CG) of the vehicle where it would exert the most effect, but instead is placed behind the CG, in line with the rear drive wheel, where it would have decreased stabilizing effect.
In U.S. Pat. No. 4,691,798 to Engelbach, the outrigger mechanism is attached to the vehicle frame where it pivots upward when retracted and downward when deployed, and those described actions are coupled to an automatic system controlled by a microprocessor guided by a rate gyro sensor. While no mechanical details regarding the construction of such an outrigger mechanism was described in this patent, it is clear that an outrigger system of sufficient track width for satisfactory stabilization when pivoting up to down or vice-versa on both side of the vehicle can interfere with traffic on either side of the vehicle, therefore limiting this vehicle's utility in the solution for an ever-increasing traffic congestion problem. And, like the previously-described invention, this design's outrigger system is also placed in line with the rear wheel of the vehicle, thereby limiting its stabilizing authority.
In U.S. Pat. No. 4,133,402, a simple outrigger assembly of narrow track base was described attached to the rear wheel of the vehicle, and therefore, as in the two previous patents, its stabilizing ability is limited.
In U.S. Pat. No. 5,048,864 by Geiger dated Sep. 17, 1991, a similar outrigger system was described which was very much similar to that of Archers in that the outrigger system is placed transversely in-line with the rear wheel and not near the center of gravity of the vehicle thus significantly limiting its stabilizing authority. Furthermore, this patent requires the width of the vehicle to be nearly as much as that of a sub-compact size car (51 inches or 129.5 cm versus 60 inches or 152 cm) for adequate stability hence offers little advantage in term of road saving ability.
In my previous U.S. Pat. No. 5,401,055 (Pham), a center-tracking vehicle capable of carrying two occupants are disclosed which can overcome the aforementioned limitations of the prior arts. However, this vehicle design as illustrated does not represent the optimum in aesthetic, aerodynamic efficiency, space efficiency, cost of production, maintenance and ease and reliability in daily operation. The use of pneumatic actuators in my past design requires high pressure compressed air which is prone to leakage and is energy-consuming to produce. Furthermore, my past design requires a large outrigger telescopic strut in order to house the entire outrigger wheel in order to retract the outrigger wheel past the center of gravity of the vehicle. This previous design requires a separate pneumatic actuator for retracting the outrigger wheel. To reduce the length of this previous vehicle, the driver is required to sit fairly high, on top of the flat engine. This increases the vehicle height and hence vehicle's profile area, and developing a new flat engine and separately rear-mounted transmission for this vehicle requires major development expenses. To reduce the vehicle's profile area, the top area above the rear passenger is removable, but this requires extra effort, thus not very ergonomically appealing. Therefore, my previous design is heavy, expensive, ergonomically undesirable and prone to failure.
My new design that is herein disclosed will represent a major improvement in all of the above aspects, with emphasis on simplicity and reliability of the outrigger mechanism and of the engine-transmission arrangement, on practicalities such as ease of entry and exit with automobile's style doors, and improved aerodynamics and aesthetics. The new design uses an off-the-shelf in-line motorcycle engine-transmission unit that requires almost no developmental expenses. Its outrigger struts are very simple hydraulic actuators that are much more resistant to leakage than the pneumatic actuators, and its ski-rollers at the end of the outrigger struts can be easily retracted above the vehicle's center of gravity in order to lift the vehicle upright should it fall on its side. The ski-roller provide stable support for parking in soft surfaces such as snow, sand, gravel, mud or grass while a typically small-size outrigger wheel would be more likely to sink, making the vehicle liable to fall over.
A very important advantage of the herein-disclosed design over the prior arts is in the location of vehicle's engine-transmission unit and seating arrangement. Most of prior art designs feature a single-seat vehicle, with the engine usually located behind the seat. This is done in order to keep the vehicle's length and height, hence the vehicle's profile area to a minimum. Otherwise, a lengthy 2-seat vehicle would have poor maneuverability and would take up too much parking space, and a light-weight vehicle with too much profile area would be very unstable in strong cross wind. In a four-wheeled automobile, the engine is located in either in front or at the rear, transversely inline with the front wheels or rear wheels, thus allowing reduction in the vehicle's length. In a center-tracking vehicle, the primary road wheels must be placed in the center line in tandem relationship, the engine then must be placed either in front or behind the primary road wheel, thus making the vehicle much longer than an automobile if the vehicle is to have two tandem seats for carrying two occupants. A few of the prior art designs that feature a two-seat center-tracking vehicles are either too tall because the occupants seat above the engine-transmission assembly in motorcycle fashion (J. Pattner, U.S. Pat. No. 2,589,023), or too long because the engine-transmission assembly is placed behind the rear seat (Horn, U.S. Pat. No. 5,181,740).